Fermented liquid milk products, such as soured milk, yogurt and crème fraîche, are commonly prepackaged and transported in disposable consumer packaging. A large number of these disposable packages are produced from a packaging laminate with a rigid but foldable paper layer and outer liquid-tight polyethylene layers, primarily of low density, on both sides of the paper layer. Such packaging containers are currently produced on an industrial scale with the help of modern rational packing machines, which shape, fill and seal prepackaged containers, based on either a material web or pre-manufactured packaging laminate sheets as starting material.
For instance, filled and sealed packaging containers are produced from a packaging laminate material web, by the web first being reshaped into a tube. This is done by joining the two longitudinal edges of the web by means of a longitudinal liquid-tight overlap seam using heat sealing. The tube is filled with the actual fermented liquid milk product, and divided into connected filled packaging units, by means of repeatedly sealing the tube across the tube's longitudinal axis below the tube's product level. The packaging units are separated from one another by means of cuts in the transverse sealed areas, and are finally given the desired geometrical shape, typically parallelepipedic, by means of at least one additional shaping operation.
Alternatively, in a corresponding manner, filled sealed packaging containers are produced from a substantially rectangular, flat-folded tubular material out of the packaging laminate, by the material first being raised to an open tubular container capsule. One of the container capsule's open ends (e.g., the bottom end) is sealed by fold forming and heat-sealing of foldable connected end panels at the bottom end of the container capsule. The container capsule, now provided with a bottom, is filled with the fermented liquid milk product in question through its open end, and is then sealed by fold forming and sealing of the corresponding foldable and connected end panels at the top end of the container capsule.
The common types of packaging containers, regardless of whether they are produced from a material web or from pre-manufactured material sheets or blanks out of the packaging laminate, are generally provided with some form of opening device in order to facilitate access to the packaged milk product when it is time to empty the packaging container of its contents. Such an opening device can either be a completely or merely partially integrated part of the packaging container. In a very simple, but effective and well-functioning example of a design, an opening device of the type first mentioned above could consist of a tear perforation, along which a limited area of the container wall, delimited by said tear perforation, is intended to be torn off and removed, thus exposing and emptying hole through which the packaged product can be poured when the packaging container is to be drained of its contents.
The common type of packaging container has many advantageous and appreciated characteristics. It is easy to stack and arrange such containers in ways which enable efficient transportation and handling, and they provide the product with an excellent mechanical and physical protection for the entire duration of transporting and handling the packaging container, from filling and sealing to emptying and consumption. The packaging container is furthermore mechanically stable enough to be able to be easily picked up and held by hand when it is time to open it and consume its contents.
A drawback associated with the common type of packaging container, however, is that it practically always leaves a non-negligible amount of the fermented milk product remaining on its inner walls after it has been emptied. In the case of soured milk, for instance, it is not unusual for the amount of product remaining in the package to make up approximately 10% of the original amount in the packaging container, while the corresponding remaining product amount for crème fraîche can make up as much as 20% of the original product amount.